The present invention relates to signaling protocols in telecommunications networks. More particularly, the present invention relates to a telecommunications network that employs an asynchronous transfer mode (ATM) signaling protocol to transport bearer control signaling messages and a synchronous transfer mode (STM) signaling protocol to transport call control signaling messages.
Typically, networking systems employ what is known as a layered architecture. In a layered architecture, data and/or signaling messages are transferred between peer entities at the same level of the layered architecture with the help of the services provided by the underlying layers. The messages exchanged between the peer entities are generated, formatted, transmitted, received and otherwise transported according to the rules described in a protocol specification.
A simple layered architecture may include, among other layers, an application layer, a network layer, a data link layer and a physical layer. The general function of the application layer is to generate, process and format data and/or signaling that is required to support a particular user application (e.g., a cellular voice service). The general function of the network layer is to manage the links and end-to-end relationships between various network entities, for example, the various mobile switching centers, radio network controllers, and base station units in the cellular radio network. The data link layer provides for the transfer of data and signaling between adjacent nodes in the network. The physical layer provides services which are required to interface with the physical environment, such as encoding, modulating, transmitting and receiving signals.
A layered architecture, as described above, may also include a signaling layer. The signaling layer would likely be part of the application or, alternatively, the network layer. The general purpose of a signaling layer is to generate and receive signaling messages, in accordance with a particular signaling protocol. As stated previously, a signaling protocol actually defines the rules which govern the generation and format of signaling messages, which are used, for example, to set-up, maintain and release network connections (e.g., mobile telephone calls) between network entities.
The narrowband integrated services digital network (N-ISDN) user part (ISUP) system 7 is an example of a signaling protocol that is widely employed and well-known in the art. The ISUP system 7 signaling protocol generally supports synchronous transfer mode (STM) based network connections. More specifically, the ISUP system 7 signaling protocol defines a set of rules for transporting call control messages within the network, wherein call control involves functions such as, though not necessarily limited to, billing, call forwarding and caller identification.
As the ISUP system 7 signaling protocol is widely employed throughout the world, there are many national and international variations of the protocol. Accordingly, each variation differs in the specific messages and parameters used for call control. However, regardless of the variation, all include a routing label comprising an originating point code (OPC), a destination point code (DPC), signaling identifier octet (SIO) and a circuit identification code (CIC). The CIC in particular defines the time slot in a STM data frame that has been allocated to the corresponding call control message. Hence, the CIC implicitly defines the corresponding call.
The AAL2 signaling protocol Q.aal2 is another example of a signaling protocol. Unlike the ISUP system 7 signaling protocol, the Q.aal2 signaling protocol is neither widely employed nor well-known. Further in contrast with the ISUP system 7 signaling protocol, the Q.aal2 signaling protocol defines a set of rules governing the transportation of bearer control messages, wherein bearer control involves the establishment and release of network connections, particularly connections through an AAL2 transmission network.
The Q.aal2 signaling protocol also has associated with it a number of basic codes, for example, a virtual circuit connection identifier (VCCI) code and a channel identification (CID) code. In combination, the VCCI code and the CID code uniquely identify the bearer servicing the AAL2 served user at a given instant in time.
The Q.aal2 signaling protocol is incapable of independently supporting call control signaling messages. Accordingly, when transmitting calls over an AAL2 based transmission network, it would be highly desirable to utilize the call control signaling information available through other signaling protocols, such as the ISUP system 7 signaling protocol, rather than redesign the Q.aal2 signaling protocol so that it is capable of independently supporting call control messages.
The present invention involves a technique which provides call control signaling support for calls being transported over an AAL2 based transmission network. In general, the present invention accomplishes this by binding the call control signaling information, available through other signaling protocols, such as the ISUP system 7 signaling protocol, with the bearer control signaling information associated with the Q.aal2 signaling protocol, wherein both call control information and bearer control information are required to set-up, maintain, and release calls. Moreover, the present invention links the call control signaling information and the bearer control signaling information without any need to redevelop the Q.aal2 signaling protocol or the ISUP system 7 signaling protocol.
Accordingly, it is an objective of the present invention to provide call control signaling information for calls being transported over an AAL2 based transmission network connection.
It is another objective of the present invention to provide call control signaling information for calls being transported over an AAL2 based transmission network connection, supported by a Q.aal2 signaling protocol, without the need to modify or otherwise redesign the Q.aal2 signaling protocol.
In accordance with one aspect of the present invention these and other objectives are achieved by a method for setting up and maintaining an asynchronous transfer mode (ATM) connection. The method involves detecting an identification code associated with call control signaling information, wherein the call control signaling information is formatted in accordance with a first telecommunications signaling protocol. The identification code is then transferred to a second telecommunications signaling protocol, wherein the second telecommunications signaling protocol is an ATM adaptation layer type 2 (AAL2) signaling protocol, and wherein the AAL2 signaling protocol is associated with the formatting of AAL2 bearer control signaling information. Once the identification code is transferred, the call control signaling information and the identification code are transported from a source node in the telecommunications network to a destination node in the telecommunications network in accordance with the first telecommunications signaling protocol, and the AAL2 bearer control signaling information and the identification code are transported from the source node to the destination node in accordance with the second telecommunications signaling protocol. At the destination node, the call control signaling information and the AAL2 bearer control signaling information are bound together as a function of the identification code, and the ATM connection is set-up as a function of the call control signaling information and the AAL2 bearer control signaling information.
In accordance with one aspect of the present invention these and other objectives are achieved by a method for binding call control signaling information and ATM adaptation layer type 2 (AAL2) bearer control signaling information, wherein the call control signaling information and the AAL2 bearer control signaling information are required to set-up and maintain a corresponding ATM voice connection. The method involves defining a system 7 user part at a source node in the ATM based telecommunications network as an AAL2 served user, wherein the system 7 user part is supported by an integrated services digital network user part (ISUP) system 7 signaling protocol which is employed for formatting the call control signaling information. Next, the ISUP system 7 signaling protocol invokes a Q.aal2 signaling protocol, wherein the Q.aal2 signaling protocol is responsible for formatting the AAL2 bearer control signaling information. A circuit identifier code (CIC) from the system 7 user part is then transferred to the Q.aal2 signaling protocol, wherein the CIC uniquely identifies the call control signaling information. Next, the call control signaling information and the CIC are transported from the system 7 user part in the source node to a peer system 7 user part at a destination node in accordance with the ISUP system 7 signaling protocol, and the AAL2 bearer control signaling information, the CIC, and a connection identifier (CID) code are transported from the source node to the destination node in accordance with the Q.aal2 signaling protocol, wherein the CID code identifies the ATM voice connection. At the destination node, the CIC is transferred from the Q.aal2 signaling protocol to the system 7 user part, and the system 7 user part is informed that an AAL2 transmission connection has been established. Finally, the call control signaling information and the AAL2 bearer control signaling information are aligned, thereby establishing the ATM voice connection as a function of the CIC and the CID.